The present invention relates to an ignition timing control apparatus for controlling the ignition timing of an engine by an electronic control.
It is well known in the art that during the acceleration condition of an engine the engine speed varies considerably and therefore in order that the ignition timing may be controlled optimally it is necessary to provide an acceleration correction when estimating an engine speed. Apparatus have been proposed in the past in which such acceleration correction is provided by using two ignition cycle times (e.g., Japanese Patent Publications No. 51-45002 and No. 61-37457).
However, this type of known ignition timing control apparatus requires at least two ignition cycle times to provide the necessary acceleration correction during the acceleration operation of an engine.
Therefore, a time is required until the acceleration correction is provided. This gives rise to a problem that when the engine comes into an acceleration condition, the accuracy of the engine speed estimation is lowered due to the delayed acceleration correction and hence the accuracy of the ignition timing control is deteriorated.
Also, apparatuses have been developed in the past in which the detection of any faulty cylinder in a multi-cylinder engine is effected in accordance with the maximum and minimum values of the engine speed during every ignition cycle so as to effect the detection with respect for example to faults in the secondary side of the ignition coil, the fuel system, etc., (e.g., JP-A-61-258955).
This type of apparatus is disadvantageous in that since the maximum and minimum values of the engine speed during every ignition cycle must be detected, a signal must be generated for every small degrees of crankshaft rotation and therefore the apparatus cannot be applied to engines of the type employing a crank angle sensor which generates a limited number of pulses.